The original language and your translation on every YouTube™ video — a single, non-overlapping layer that switches cleanly, sentence by sentence. Free and open source.
Also works on Edge同样支持 Edge·Chromium 111+Chromium 111+·no account本扩展无需注册·runs locally本地渲染
youtube.com/watch
100% free完全免费MIT licensedMIT 许可No tracking无追踪No account to create本扩展无需注册Renders locally本地渲染Open source开放源代码
How it works工作原理
Three steps to bilingual captions
三步开启双语字幕
It reads the video's real caption track, translates it, and renders both languages in one tidy overlay you can style and drag.
它读取视频真实的字幕轨道，翻译后把两种语言渲染在同一层整洁的字幕里，样式可调、位置可拖。
01
Pick your language pair
选择你的语言组合
Pick a target language in the popup — 50 are available, and you decide which of them appear in the menu — and which translation engine to use. A live preview shows the result as you tweak.
Press play on any YouTube™ video. Captions turn on automatically, and the player-bar button toggles the overlay on or off.
在任意 YouTube™ 视频上点击播放。字幕会自动开启，播放栏上的按钮可随时开关字幕层。
03
Read both lines
同时读两行
The original language sits on one line, your translation on the other — one non-overlapping layer that switches sentence by sentence.
原文占一行，你的译文占另一行——同一层字幕互不重叠，逐句切换。
Single layer · never overlaps单层显示 · 永不重叠
No more subtitle soup
告别字幕一团糊
Other tools stack a second track on top of YouTube's own captions and they collide into a blob. This extension hides YouTube's native layer and renders one clean overlay instead.
Two free engines, plus your own key两套免费引擎，也可自带 Key
Translation that lines up with what you hear
和你听到的对得上的翻译
Use YouTube™'s own whole-track translation — one request for the whole track, aligned cue for cue — and when a track can't be translated, fragmented captions are rebuilt into full sentences before Google translates them. Bring your own API key and each sentence is understood whole, then split back across the subtitles.
使用 YouTube™ 自带的整轨翻译——整轨只要一次请求，逐条对齐——视频不支持翻译时，会先把碎片字幕拼回完整句子，再交给 Google 翻译。也可以填自己的 API Key：整句理解之后再按字幕切回来。
Primary首选YouTube™ whole-trackYouTube™ 整轨翻译
Aligned to the video's timing, and it arrives with the line.
与视频时间轴对齐，和原文一起出现。
Smart智能Smart sentences (Google)智能整句（Google）
Rebuilds fragmented captions into full sentences before translating — also selectable manually.
先把碎片字幕拼回完整句子再翻译——也可以手动选用。
Fully customizable高度可定制
Style every line exactly how you like
每一行都按你的喜好来
Set per-line font, size, text color, background color and opacity, outline, and line spacing — and choose which line sits on top. A live preview in the popup shows every change instantly.
Per-line font, size, and text color每行独立的字体、字号和文字颜色
Background color and opacity, outline, and line spacing背景颜色与透明度、描边和行间距
Choose which line sits on top, with a live preview选择哪一行在上，带实时预览
50 target languages50 种目标语言
Draggable · one-click toggle可拖动 · 一键开关
Put the subtitles wherever you want
字幕想放哪就放哪
Grab the handle and drop the subtitle box anywhere on the video — it stays put. Double-click to reset, and it works in fullscreen too. A button in the player control bar turns the overlay on and off.
Drag anywhere, position persists; double-click to reset随意拖动，位置会被记住；双击复位
Works in fullscreen支持全屏
Player-bar toggle: blue when on, grey when off播放栏开关：开启时为蓝色，关闭时为灰色
Export to SRT导出为 SRT
Take the subtitles with you
把字幕随身带走
Download the current video's subtitles as a standard .srt file — the original language, the translation, or both together as a bilingual file. With your own API key it can translate the whole track for you, and it says how many requests that will take before it starts.
把当前视频的字幕下载为标准的 .srt 文件——可选原文、译文，或两者合并成一份双语文件。填了自己的 API Key 之后，还可以让它整片翻译，开始前会先告诉你大约要几次请求。
subtitles.srtOriginal原文Translation译文Bilingual双语
1
00:00:04,120 --> 00:00:07,480The best ideas start as questions.最好的想法都始于提问。
Yes. There are no analytics, no tracking, and no accounts. Caption text is sent only to the translation service you choose — nothing else leaves your browser. The extension is open source under the MIT license, so you can verify this yourself.
私密。没有任何统计分析、追踪或账号。字幕文本只会发送到你自己选择的翻译服务——其余内容都不会离开你的浏览器。本扩展基于 MIT 许可开源，你可以自行核实。
Which browsers does it work on?它支持哪些浏览器？
Chrome, Edge, and other Chromium-based browsers on version 111 or newer. It's a Manifest V3 extension. You can install it from the Chrome Web Store, or load it unpacked from the source on GitHub.
支持 Chrome、Edge 以及其他基于 Chromium、版本 111 或更高的浏览器。它是一个 Manifest V3 扩展。你可以从 Chrome Web Store 安装，也可以从 GitHub 上的源码以未打包方式加载。
Does it cost anything?它收费吗？
No. It's completely free and open source under the MIT license. There's no paid tier, no subscription, and no account to create.
不收费。它完全免费，基于 MIT 许可开源。没有付费档位、没有订阅，也不用创建账号。
Does it work with auto-generated captions?它支持自动生成的字幕吗？
Yes. It reads the video's real caption track, and it can turn captions on for you automatically. If needed, it also falls back to reading the on-screen caption text, and it survives YouTube's single-page navigation.
No — the video itself is untouched. YouTube™'s whole-track translation arrives with the line, and the Smart sentences engine prefetches ahead of playback, so the second line usually keeps up; when a service is busy it shows an honest “…” rather than a stale line. Lines are rendered from the timed cues, so they switch by whole sentence without flicker.
The subtitles cover the video — how do I move them?字幕挡住画面了，位置怎么调？
Hover the subtitle box and drag the little round handle at its top-left corner to put it anywhere on the video — the position is remembered per device, and double-clicking the handle resets it. The popup also has top / center / bottom presets, plus per-line font size and spacing. Since v3.5.0 the box automatically steps above the progress bar while the player controls are visible.
Why do translations sometimes pause or not show up?为什么翻译有时不出来、或者停一下？
The Smart sentences engine uses Google's free public endpoint. Under heavy use — long videos, lots of seeking — it may briefly rate-limit. The extension notices, slows down and retries on its own: the translation line shows "…" while it waits, and translations resume automatically, usually within seconds to a couple of minutes. Already-translated sentences stay cached. YouTube's own whole-track translation can be limited too — when that happens the extension falls back to the sentence engine and comes back for the whole-track version a little later.
智能整句引擎走的是 Google 免费公共接口，重度使用（超长视频、频繁拖进度条）时可能被短暂限流。扩展会自己发现并放慢重试：等待期间译文行显示「…」，翻译通常在几秒到一两分钟内自动恢复。已翻译过的句子有缓存不受影响。YouTube 自带的整轨翻译同样可能被限流——真遇上时扩展会先用整句引擎顶上，过一会儿再回头去要整轨译文。
Is the feature I want planned?我想要的功能有没有计划？
The roadmap says what is planned, what is being built, and what is not happening yet — with the reason for each. If what you want is not on it, say so: most of what is on that list started as somebody's message.
